This invention concerns a system for controlling the reading timing in a number of solid state image sensors in an optical reading device in which the surfaces of an original object, e.g., a document, is divided into a plurality of regions and different solid state image sensors are allocated to each of the respective regions to thereby read picture images. In a typical device, the image sensor is of the scanning type made up of a plurality of sensing elements which are sequentially energized to each provide an image signal corresponding to a respective portion of the overall image. If a plurality of a solid state image sensors are used, each of which is made up of a plurality of individual sensing elements which must be scanned, there are some possible advantages in terms of image quality, but problems are encountered in making sure that the regions covered by each of the image sensors are continuous at the boundaries and that a proper timing sequence is maintained for the scanning operations.
More particularly, reading devices adapted to conduct successive line reading using a plurality of solid state image sensors (hereinafter referred to simply as sensors) are advantageous over reading devices using only one sensor, since the optical distance between the sensor and original can be shortened and optical distortion is decreased, but multiple sensor devices are disadvantageous in that they are more difficult to fabricate. More specifically, two types of adjusting procedures have been required in the fabrication of conventional reading devices, (1) an adjustment to ensure that the video signals outputted from each of the sensors is continuous at the boundary between each of the regions, and (2) an adjustment to insure that the image regions to be read by each of the sensors coincides with the corresponding region of the original to be read. Such adjustments, either mechanical or electrical, have been very difficult to accomplish satisfactorily since the adjusting procedure for one of them may impair the result of the adjusting procedure for the other.